Under tight security, Pakistan's top court is to deliver a much-awaited decision on Thursday on corruption allegations against Prime Minister Nawaz Sharif's family which could determine his political future.

If the Supreme Court announces punitive measures against Sharif or his family members as part of the decision, it may lead to a crisis in government. In 2012, the same court convicted then-Premier Yusuf Raza Gilani in a contempt case, forcing him to step down.

Thursday's decision will be the outcome of petitions from opposition lawmakers dating back to documents leaked in 2016 from a Panama-based law firm that indicated Sharif's sons owned several offshore companies.

Sharif's family has acknowledged owning offshore businesses.

The opposition wants Sharif, in power since 2013, to resign over tax evasion and concealing foreign investment. Sharif has defended his financial record.

Information Minister Maryam Aurangzeb told reporters the government will "accept the court decision."

Naeemul Haq, a spokesman for cricketer-turned-politician Imran Khan, whose party is leading the petition, said the decision will be an "historic one."

Lawyer A.K. Dogar, who is not involved in the probe by the Supreme Court or the petition, said the decision could determine the political fate of Sharif.

Senior opposition politician Mehnaz Rafi, from Khan's party, told The Associated Press she hopes the decision will help recover tax money from Sharif's family and others who set up offshore companies to evade taxes. If the court finds Sharif's family evaded paying taxes, she said he should resign as he will no longer have "moral authority to remain in power."

The prime minister has insisted his father built up the family business before Sharif entered politics in the 1980s. Sharif says he established a steel mill abroad while he was exiled to Saudi Arabia by former military ruler Pervez Musharraf, who seized power in a coup in 1999.